Although to really improve the performance of the GT's exhaust you need to replace the narrow, restrictive piping and the stock muffler (as in a catback system), some people just want a sportier sound. The answer is a performance muffler. These are pretty much universal fit but one brand seems to be used successfully on the GT most often... Magnaflow. The nice thing about the Magnaflow is that at normal speeds it's fairly quiet but, gun it, and the thing puts out a nice deep, rich sound. Not like some of those mufflers that make the engine sound like a weedwacker on steroids! For the money, Magnaflow's can't be beat. Click here to order one at a discount price!